To optimise recovery, the oil industry depends on gathering data from wells and reservoirs. Such data forms the basis for nearly every decision with respect to the development and operation of an oil field, including where to locate new wells, maintenance programs and allocation/control of production.
In view of this need for data, many well applications are completed with permanently installed downhole instrumentation, such as pressure and temperature monitoring devices. Due to the generally harsh wellbore environment, permanent instrumentation has a limited lifetime and there is an expectancy of failure. Such failure leads to limited obtainable information from the reservoir and limited control possibilities. This may have a serious impact on the understanding and modelling of the reservoir and reduce the reservoir recovery factor.
Furthermore, known installations typically require electrical supply and communication lines running the length of the production tubular from the wellhead down to the downhole monitoring and/or control system, said lines normally being secured to the production tubular using tailored clamps. Fitting cables to the tubing is a time consuming activity that prolongs the installation time. During the installation and use of equipment such as traditional downhole pressure and temperature sensors, the cables, clamps, splices, penetrators, connectors and the like may become exposed to well fluids and are natural failure nodes. If damage occurs, the worst-case scenario is that the entire length of tubing must be retrieved to replace a damaged cable. If the damaged equipment is repairable, a well service operation must be performed.
Other borehole devices, such as multiphase flow meters, sand detectors, valves, chokes, circulation devices and the like may also be installed as part of a permanent borehole completion, and where this is the case similar problems as described above apply.
Depending on the well conditions, the lifetime expectancy of permanent installed equipment may range from a few months to a few years, and as noted above should permanent equipment fail, the only remedy in most cases is to re-complete the well, meaning replacing the production tubular and associated systems. This operation entails high risk and cost and is generally very undesirable.
Retrofit downhole monitoring and/or control systems are desirable in the art for use in the event of failure or compromise in permanent monitoring systems, thus permitting the continuity of dataflow from the well to be regained/maintained. In addition to such retrofit solutions, there is a recognised desire for downhole monitoring and/or control systems that are easily installed, retrieved and maintained, in order to provide for a long-term monitoring and/or control functionality in harsh well conditions.
WO 2006/041308 describes systems for downhole data acquisition and wireless data transmission in a well, and wireless downhole control systems enabling remote wireless flow control of downhole production and/or injection zones in a well related to the production of hydrocarbons. Specifically, operation of a restricting valve element in the pipe flow can be used to send a wireless telegram in an oil or gas well, i.e. wireless signal transmission is achieved by transmitting pressure pulses via flowing fluid.